IS ACID-PHOSPHATASE-ACTIVITY PRESENT IN BONE-MATRIX AT SITES OF ENDOCHONDRAL OSSIFICATION IN RABBIT FRACTURE CALLUS

It has been suggested that acid phosphatase activity is present in new ly formed bone matrix at sites of endochondral ossification in rabbit fracture calluses. Because acid phosphatases are usually found intrace llularly, it was decided to test this possibility more rigorously. Tis sue from 10- and 14-day healing rabbit fractures was subjected to a se ries of critical tests for acid phosphatases with a pH optimum of 5.0. Fluoride, tartrate and molybdate were used as potential inhibitors of acid phosphatase activity. The effects of-several counterstaining pro tocols were also investigated. A fluoride- and tartrate-resistant acid phosphatase is located in osteoclasts and mononuclear phagocytes. Dif fuse staining of the bone matrix is seen, but it is dependent upon the length of incubation in the substrate medium and the distance from th e acid phosphatase-reacting cells. It is concluded that the coloration of the bone matrix is probably caused by diffusion of the dye and rea ction product and is, therefore, artifactual. (C) 1998 Chapman & Hall.